Insecticide synergists are compounds which, although having no direct toxic effect at the dosage employed, are able to substantially enhance the observed toxicity of an insecticide with which they are combined. For example, Wilkinson, Metcalf, and Fukuto, Journal of Agricultural and Food Chemistry, Volume 14, No. 1, pages 73-79 1966, found that certain methylenedioxyphenyl compounds gave synergistic kill of the common house fly when combined with 1-naphthyl N-methylcarbamate, 3,4-dimethoxyphenyl N-methylcarbamate, and 4-di-methylamino-3,5-xylenyl N-methylcarbamate.
Georghiou and Atkins, Jr., Journal of Agricultural Research, Volume 3, No. 1, pages 31-35 1964, demonstrated that piperonyl butoxide increased the toxity of SEVEN, Zectran and B 37344 (4-methylthio-3,5-xylyl N-methylcarbamate) to honeybees (Apis mellifera).
Although the aforementioned referencesindicate that a synergistic effect is obtained when certain compounds are combined with specific known insecticides, there is no broad teaching that such compounds would have the same effect when mixed with other insecticides.
For example, U.S. Pat. Nos. 4,173,637 and 3,748,356 disclose that the mixtures of the compounds described in these two patents with other insecticides, miticides and plant growth regulators sometimes produce synergistic effects. However it has been observed that mixtures containing Dimilin or N-(2-chlorobenzoyl)-N'-[4(3,5-dibromopyridyl-2-oxy)phenyl]urea, two compounds described in U.S. Pat. Nos. 3,748,356 and 4,173,637, respectively, and piperonyl butoxide do not produce synergistic kill of many insects, such as the armyworm.
Moreover, to attempt to determine which synergist would be effective with which insecticide by a trial and error technique is beyond the economic capability of most research laboratories. Hence, it was indeed unexpected and surprising to find that methylenedioxyphenyl derivatives were effective synergists when employed in admixture with certain benzoyl urea insecticides. Thus, according to the present invention it was found that the amount of benzoyl urea insecticide can be greatly reduced resulting not only in economic savings but more importantly protecting the natural environment as well.
Accordingly, one or more of the following objects can be achieved by the practice of this invention. It is an object of this invention to provide novel insecticidal compositions which contain mixtures of a synergist and certain benzoyl ureas. Another object of this invention is to provide insecticidal compositions containing mixtures of piperonyl butoxide and cerain benzoyl ureas. A further object is to provide insecticidal compositions wherein the active toxicant can be employed in a reduced amount and still achieve the desired insect control. A still further object of the invention is to provide a method for controlling insect growth by the application of the composition of this invention. Those and other objects will readily become apparent to those skilled in the art in the light of the teachings herein set forth